Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
import sys
H, W = [int(x) for x in input().split()]
s = [list(input()) for _ in range(H)]

white = sum([s[i].count('.') for i in range(H)])
que = deque([(0, 0, 0)])
s[0][0] = '#'
while que:
    y, x, d = que.popleft()
    if (y, x) == (H - 1, W - 1):
        break
    for dy, dx in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
        ny = y + dy
        nx = x + dx
        if ny < 0 or ny > H - 1 or nx < 0 or nx > W - 1:
            continue
        if s[ny][nx] == '#':
            continue
        s[ny][nx] = '#'
        que.append((ny, nx, d + 1))
else:
    print(-1)
    sys.exit()

print(white - d - 1)